I was sat in my car recently watching many aircraft in the sky making patterns with their emmissions. One that stood out was a fairly acutely curved one. At first it appeared to start in alignment with the partion that divided the front and back window of my car. After about 15 minutes it had travelled way past the partion and was then at the back of the car. Its form remained as original, ie the wind movement had not displaced its shape. Can someone please explain how this occurred.